Where did you come from? (AKA: Why don't I clean more?)
I have a small compost bucket that I keep under my kitchen counter until it is ready to be taken out. That means it sits there for probably two weeks, collecting my tea leaves and kitchen scraps, and half a pint of blueberries I swore I would eat. It is fairly well sealed so it’s not like it is stinking up my house. It does manage to attract quite a few fruit flies though. Fruit flies are a challenge to control because most treatments can only get to a few adults, but can’t get to the larvae. What’s there to do?
If you have ever had, or dealt with a fruit fly problem, you know the things seem to just appear all of a sudden. I had nothing yesterday, but today I open the lid and a few adults fly out, pupae are secreted in the edges of the lid, and if I look close, the larvae are digging around in the scraps. They didn’t just appear there, they came from Africa. Okay, they originated from Africa sometime around 10,000 years ago. They were attracted to fruits, which early humans collected and stored in their caves. Fast forward to now, they are on my fruits in my kitchen. And my kitchen compost bin that sits there for a week longer than it probably should is not much different from those caves: researchers found 24 million discarded fruit pits in one cave!
We know they are attracted to rotting fruits, and the little buggers reproduce fast. Under normal room conditions, fruit flies develop in about ten days and females lay hundreds of eggs. So all you need is one mated female and a little over a week later, you literally have hundreds. Then those mate and the population grows exponentially. My little compost bucket is a fruit fly breeding ground. Commercial kitchens and anywhere fruits and veggies are stored are like a homing beacon and all-you-can-eat buffet to nearby fruit flies. Once they check in, they never really leave.
This quick life cycle and ability to lay lots of eggs has made them a model organism for science, particularly genetic work. So fruit flies can do some good…
Fruit flies are good at what they do. They do form social groups, that’s why you so often find lots of fruit flies in one general area. They are most active in the morning and like warm temperatures, but they will find areas to hide in if temps get too hot. As previously mentioned, the larvae get into the food, or junk, or whatever wet organic material they can find and are protected inside while they chow down and develop. How do you get a treatment underneath all that food buildup inside a drain? You don’t.
I’ve always heard that small flies don’t fly very well, they typically are found close to their food source and breeding grounds. New research is shedding some very different light on that subject.
A fruit fly takes just 16 minutes to fly 0.6 miles (1km)
A well fed fruit fly has enough energy to fly for 3 hours
Outdoors, fruit flies were found over 9 miles (15km) from their release point
With a breeze, they can potentially fly even further
So where did my fruit flies come from? They may have come from outside, maybe from my compost bucket if I didn’t get it totally washed out last time, or maybe from somewhere else in my kitchen. (I’ve left that tomato on the counter way too long…). In a restaurant, or hotel kitchen, or hospital they could have come from any number of sources. The challenge becomes eliminating them: finding their indoor sources, disposing of them, and cleaning them up. If I take my compost bucket out weekly instead of every two weeks, clean it out really well so they are no leftover eggs or larvae, and keep it well sealed when there is food in there, I won’t have as much of a problem. But then what would I write about?
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Lagniappe – Drosophila melanogaster is considered the common fruit fly, but there are over 1,450 described species of Drosophila in the world and many other pest species of small fly to contend with.